Electric system



g- 1949- i H. E. EDGERTON 2,478,905

ELECTRIC SYSTEM Original Filed Aug. 16, 1953 HEIEQTOR @argd 8 ATTORNEY Patented Aug. 16, 1949 UNITED STATES PATENT OFFICE 685,501. Divided and this application February 16, 1944, Serial No. 522,662

1 The present invention, though having fields of more general usefulnms in electric systems, is particularly related to electrical-energy fiashproducing devices and strobosoopes, and to the production of intermittent or flashing light. The present application is a division of application Serial No. 685,501, filed August 16, 1933.

In the said application, there is disclosed a new and improved system for producing strong and intense substantially uniform pulses of electric energy, which may, for example, be utilized for the production of light flashes, by charging or discharging a condenser quickly. reliably and accurately at lllrfrequency through a gaseousconductor device. That feature of the invention that relates to the production of the pulses during the charging of the condenser is claimed in the present application.

The invention will now be described in connectlon with the accompanying drawings, the single figure of which is a tie view of circuits and apparatus arranged and constructed according to one embodiment of the invention.

As described in the said application, a luminescent vapor electric gaseous-discharge flash lamp or fiash tube 2 or I is provided with two internal main or principal electrodes 4 and I in a glass-tube envelope.

For reasons that will hereinafter appear, the first tube I may be referred to as a stroboscopic charging rectifier tube and the second tube 2 as a stroboscopic discharging rectifier tube. As these tubes 2 and I are identical, however, it will sufiice to describe only one of them. They may be of the normally non-conductive rectifier type described in Letters Patent 2,181,879, of December 5, 1939', reissued as Letters Patent 22,123. June 23, 1942, and Letters Patent 22,260, February 2, 1943. Reference may be made to the said Letters Patent for details. Other means than the lilustrated tube 2 orl mayalsobeusedinaccordanee with the present invention. The principal electrodes 4 and i of the gaseousconductor tube 2 define a normally ineffective principal-current path for the tube 2 and the principal electrodes 4 and l of the gaseousconductor tube 1 define a normally ineffective principal-current path for the tube I.

The gaseous-conductor means 2 or I is described in the said application as of the lowimpedance mercury-arc gaseous-conductor yp the internal electrode 4 being shown as in the form of a liquid pool of mercury, used as a cathode, and the internal electrode I serving as the anode or plate. The remarks throughout this 56 12 Claims. (01. 315-261) specification concerning mercury-arc tubes or lamps apply equally well to the tubes or lamps filled with other gases, with or without mercury vapor.

The pressure of the mercury or other gas or vapor in tubes of this nature is normally of such value as to render the gaseous-conductor means 2 or I normally non-conductive, deenergized or ineflective. The gas may become ionized, however, in response to the energization of a normally unenergized control-grid triggering or starting electrode III, to facilitate the rendering conductive or the starting of the tube 2 or I, by initiating current flow in the principal-current path including the gaseous medium of the tube 2 or 'I defined by the principal electrodes 4 and 8. This initiation and starting are eifected through the medium of a control or starting current path extending from the starting electrode III. e The electrode Ill is shown in the said application as an external metal-band condenser electrode, situated around the'glass of the envelope of the lamp 2 or 1, outside the mercury pool 4, opposite to the meniscus of the mercury. Other types of control-grid or starting electrodes, including electrodes of the internal type, may also be employed.

Direct-current voltage is shown as derived from any desired conventional source of alternating energy of suitable voltage and frequency, through a transformer. The primary winding I of the transformer is shown connected to the alternating-current source, and the secondary winding I" to the anodes of two thermionic or gaseousdischarge half-wave rectifier-tube units 20 and 22 of a common conventional type of full-wave rectifier-and-filter arrangement. The positive terminal of the rectifier source of energy is represented by the cathodes of the rectifiers 2| and 22, and the negative terminal is disposed at an intermediate tap of the secondary winding ill of the transformer. Impedances 22 and 22a and a reservoir condenser 25 are shown connected in series between these positive and negative terminals across a filter condenser 24, which may constitute part of the conventional source of direct current. A continuous supply of directcurrent energy is thus continuously maintained between the positive and negative terminals of the reservoir condenser 25. A lead conductor II is connected to the positive terminal of the reservoir condenser 2| and a lead conductor H is connected to the negative terminal at times when normally non-conductive tube I is rendered conductive.

A main discharge capacitor or condenser 26 is connected to the terminals of this reservoircondenser source 26 of direct-current potential, in series with the gaseous-conductor means 1 in the principal-current path of the gaseous-conductor means, in order normally to charge the capacitor or condenser 26 with energy at a predetermined rate from this source 25 when this principal-current path is rendered effective. Ac-

cording to the embodiment of the invention herein illustrated and described, the capacitor or condenser 26 is connected to the source of directcurrent potential 25 in parallel with the gaseousconductor device 2, so that the capacitor 26 is connected between the principal electrodes 4 and 6 of the discharge device 2. These principal electrodes 4 and 6 are therefore connected to the terminals of the condenser source 25 of energy at the same time that energy is supplied to the condenser 26 from the source 25 of direct current. The positive terminal of the condenser 26 is connected to the positive terminal of the reservoir condenser 25 by the lead conductor I0, and to the anode electrode 6 by a lead conductor 9; and the negative terminal of the condenser 26 is connected to the cathode electrode 4 by a lead conductor 8, and to the negative terminal of the reservoir condenser 25 at times when the normally non-conductive tube 1 is rendered conductive.

4 A resistor I48 is connected in parallel with the reservoir condenser 25 to discharge the circuit when the power is turned 01f. The condenser 25 should be large in capacity when compared to the flash condenser 25. Also, the condenser 25 should be of a type that has low internal impedance so that the current surges can be produced to produce short flashes of light as may be required for stroboscopic purposes.

The charging circuit for the condenser 26 may be traced from one terminal of the reservoir condenser 25 by way of the conductor I0, and through the condenser 26 and the resistor I49, in parallel, to the anode 6 of the tube 1; then through the mercury vapor of the tube I to its cathode 4; and then, by way of the conductor II, to the other terminal of the reservoir condenser 25. When the tube I is deenergized, the condenser 26 is effectively disconnected from the reservoir condenser 25.

Energy is thus fed to the condenser 26 from the source of direct current, to charge the condenser 26, in the form of current pulses that flow through the charging tube I. This energy is fed through the impedance of the wires I and I I, creating a difierence of potential between the cathode 4 and the anode 6 of the tube 2. Before each flash, the condenser 26 is charged from the direct-current source so that the anode is positive. The usual voltage to which the condenser is charged is from 200 to 2000 volts. I

The quantity of stroboscopic light is determined by the amount'of energy in the condenser 26 and by circuit conditions. The capacity of the condenser 26 is increased until there is sufllcient average light for the particular frequency of flashing and the extraneous illumination. Slow speeds require a larger amount of light per flash than fast speeds to give the same average illumination. It is necessary to have very bright flashes when the speed of flashing is slow.

After becoming thus charged, the condenser 26,- as will presently be more fully explained, may

be discharged through the gaseous medium of the tube 2, :between the anode 6 and the cathode 4. The discharging circuit for the condenser 26 is shown extending from the positive terminal of the condenser 26, by way of the lead conductor 6, to the anode electrode 6 of the tube 2; then, through the gaseous medium of the gaseousconductor tube 2, to the cathode electrode 4; and from the cathode electrode 4, by way of the lead conductor 6, to the negative terminal of the condenser 26. The cathode 4 and the anode 6 of the gaseous-conductor device 2 are thus connected by the lead conductors 8 and 6 to the condenser 26. Because of the direct metallicwire connection, the condenser 26 is enabled to discharge with relative rapidity through the gaseous-conductor tube 2 between the anode electrode 6 and the cathode electrode 4 when the gaseous-conductor tube 2 becomes conductive.

The discharge current thus obtained from the condenser source 2601 energy results in the production of an electric-energy pulse through the tube 2. This results in the production of a light flash of high illumination intensity and short duration through the tube 2.

The discharge of the condenser 26 through the condenser-discharge circuit above described is initiated by energizing the normally unenergized starting electrode I00, to apply a potential between this electrode I00 and the principal cathode electrode, under the control of a trip circuit. The trip circuit is shown comprising a normally nonconductive-or ineffective gaseous-discharge trigger tube device I40, a small auxiliary capacitor or condenser 28, a second suitable direct-current source of energy, such as a second battery I 0| or some rectified source of alternating energy, for charging the small auxiliary condenser 26 at a predetermined rate, and a normally inefiective triggering or trip flash transformer 36.

For deflniteness, the larger flash condenser 26 may be referred to as a first condenser, and the small auxiliary condenser 28 as a second con-' denser.

The gaseous-conductor device I is provided with a similar trip circuit the elements of which are designated by the same reference numerals, with the additional letter a.

The gaseolls-discharge device I40 or I40a may be constituted of a mercury-vapor thyratron, a gas-filled hot-cathode thermionic tube, a gridcontrolled cold-cathode arc-discharge tube or any other suitable discharge device. The transformers 30 and 30a. may be of the high-ratio step-up or any other desired type, with a relatively low-impedance primary winding 36 or 66a, and a secondary winding 29 or 29a, shown connected between the cathode 4 and the external electrode I00. The before-mentioned startingcurrent or control path of the tube 2, extending from the starting electrode I00 to the cathode 4, includes the inductance of the secondary winding 29. v v

The trip circuit comprising the thyratron I40 may perform its function of initiating the discharge of the condenser 26, through the abovedescribed discharging circuit, by converting the direct current of the source 25 of potential into very sudden voltage pulses in the primary winding 36 of the flash transformer 30. These, as will be described more fully presently, will be manifested as alternating-current pulses in the secondary winding 29.

Each of the trip circuits is provided with a normally unenergized control input circuit and an output circuit. The output circuits of these trip circuits, or of the thyratrons I40 and I40a, may be traced from the cathode 40 or 400, throughthe small second condenser 20 or 20a, serving as sources of energy for the respective output circuits, and the primary winding 36 or 304 of the flash transformer 30 or 30a, in series, to the anode 02 or 52a.

The control input circuits of the trip circuits may be respectively traced from the cathode 48 or 40a, through the impedance 3i or 3Ia, shown as resistors, and the secondary winding of a transformer Ii or Ila, to the control-grid electrode 50 or 000.

As soon as the normally non-conductive gaseous-discharge trigger tube I40 or I4la. of

the trip circuit is rendered conductive, the energy of the small condenser .20 or 28a is discharged through both the thyratron I40 and the primary winding 36, or the thyratron I40 and the primary winding 30a, in series.

The discharging circuit for the small condenser 20 or 20a in the trip circuit may be traced from one terminal of the condenser 20 or 200., through the tube I40 or la and the primary winding 30 or 36a, in series, to the other terminal of the small condenser 20 or 20a.

If the impedance 3i is reactive, or if there are other circuit conditions such that the grid voltage exceeds the critical starting potential, the thyratron circuit may, under certain conditions, generate its own oscillations at a frequency determined by the circuit constants and the characteristics of the tube. The impedance 3| may be made adjustable, in order to vary the charging rate of the condenser 20 and this, in turn, regulates the frequency of the high-voltage surges that are applied to the external electrode I00.

The trigger thyratron tube I40 is connected across an impedance 33, shown as a bleeder resistor, connected in parallel with the condenser 20. This resistor 33 receives energy from the battery IIII, in series with the resistor 3|, wherein power is obtained for the thyratron I40 and the condenser 28.

The bleeder resistance 33 allows a small current to flow, in order to maintain the proper voltage normally non-conductive thyratron I40 or I40a shall become conductive. This control by the grid electrode II or 50a may be exercised by suitably modifying the potential diuerence between the negatively biased control grid 00 or 50a and one of the principal or main electrodes, a the cathode or 40a, to a predetermined critical value in order to energize the normally unenergized control input circuit of the trip circuit. This may be effected by subjecting the control grid or 5041 to a suitable stimulus, as will be described hereinafter. The normally open output circuit of each of the trip circuits thereupon becomes closed or completed from the anode 52 or 52a. to the cathode 40 or 40a, in series with the low-impedance primary winding 30 or 30a and the small second condenser 20 or 20a.

The potential may be impressed upon the control electrode 50 or 00a intermittently or periodically, in. order to transmit intermittent or periodic pulses in the corresponding control or 1 there are no impulses in the grid circuits, except when used for self-oscillation, as described. A timing impulse coming into the input or grid circuit, to stimulate the grid 50, trips the thyrabias upon the grid .50. The grid 50 is connected so that it is negative with respect to the cathode 40. The resistance 33 is sometimes adjusted to prevent the self-operation of the thyratron I40 when the condenser 28 becomesfully charged. The grid 50 may be connected to various taps on the resistance 33 or 3i, respectively, to cause the thyratron I40 to oscillate as a relaxation oscillator of the self-driven type. Power is thus obtained for the thyratron I40 or M and for charging the small second condenser 28 or 28a in the output circuits of the trip circuits from the battery I01, in series with the resistor 3| or Ila. The trip-circuit-output circuit, comprising the primary winding 36 or 360., the tube 7 I40 or H00. and the small second condenser 28 or 20a, in series, may therefore be regarded as obtaining its energy from this small condenser 20 or 28a, after becoming charged from the battery m.

The conversion effected :by the trip circuits of the direct current of the battery IOI into alternating-current pulses may be effected by the before-described discharge of thesmall condenser 20 or 28a through the primary winding 36 or 36a of the flash transformer. 30 or 30a.

The control-grid electrode 50 or 50a may be tron I40, establishing a high-potential gradient between the electrode I00 and the cathode 4, thereby starting the lamp 2. The time of starting is controlled by the potential on the grid 50. The impulse is effected through the trip or grid transformer 5i when the potential of the grid 50 is raised to a certain critical value with respect to the cathode 48, in response to the stimulus applied to it, so that the light flashes are controlled in accordance with the pulses of the transformer 5i. -At each cycle, the grid 50 becomessufllciently positive with respect to the cathode 48 of the thyratron I40 to render the thyratron conductive. V

At the instant that the grid potential reaches the critical value, positive with'respect to the cathode 48, in response to the stimulus applied to the grid-50, the output circuit of the thyratron tube I '40 is completed from the anode 52 to the cathode 40, through the primary winding 30 and the condenser 28. The energy stored in the condenser 20 is then suddenly discharged through the output circuit of the thyratron tube I40, between the anode 52 and the cathode 40, and through the low-impedance primary winding 36 of the step-up transformer 30, virtually shortcircuiting the resistor 33 and placing full voltage on the resistor 3|. This very quickly and suddenly induces magnetically a high voltage for a brief interval of time in the secondary winding 29. A high voltage is thus suddenly applied to the external electrode I00. Thecathode 40 is thereupon raised to nearly the potential of the 7 face of the mercury cathode 4 and at the Junetion between the mercury and the inner wall of the glass tube. The gas in the tube becomes thereupon ionized. The bright mercury spot constitutes a source of electrons upon the mercury, in the vicinity of the cathode 4, that supplies electrons for ionizing the normally un-ionized gas in the lamp 2, to render the lamp conducting. The main discharge condenser 26 thereupon discharges its energy violently into the lamp 2, to produce an arc discharge between the cathode 4 and the anode 6 through the lamp 2. Part of. this energy is transformed into a pulse of useful light. A brilliant flash of light is, there- I fore, produced by the lamp 2 when the condenser the grid 50 controls the time of starting of the violent electrical transients that are transformed into useful light. The condenser 26 thus discharges through the mercury-pool tube 2 once corresponding to each pulse of the transformer I.

The are through the lamp 2 is not maintained, because of the action of the tube I which prevents current flow to the tube 2. The condenser 26 is again charged at a predetermined time before the next discharge, and a flash of light is obtained from the tube I.

The inductance of the conductors 8 and I0 is useful in extinguishing the arc. as it tends to make the discharge current oscillatory.

At the instant of discharge, the current surge through the lamp 2 is very great. It may be over one thousand amperes. The flash of light through the tube is very intense and quick. The apparent speed of a moving object is thus effectively reduced or stopped," since the object moves an lnappreciable distance during the time that the light. is on. Because of the low impedance '-of the mercury lamp 2, the voltage across the resistor 33 is zero, or even negative, after the condenser 26 has become fully discharged, allowing the tube to deionize; and the duration of the flash discharge is short, the time taken for the circuit to function being about 10 microseconds or less, the exact time being a function of the size of the capacity 26, the voltage to which it is charged, the dimensions ,of the tube, the temperature of the tube, the impedance of the leads 8 and I0 connecting the condenser :and the tube, the volt-ampere characteristics of the tube 2, and other factors. Under some conditions, the duration of the flash is less than one microsecond.

The pulses producing the flashes cur during times very short compared to the intervals of time between the pulses and flashes.

As the thyratron I40 is a rectifier, the current in the circuit comprising the condenser 28 and the transformer 30 cannot oscillate, although there is a tendency to doso. At the instant that the current stops, due to the oscillation, the tube I40 begins to deionize, since the grid and plate voltages, at this instant, are both either negative or. zero with respect to the cathode 48. The charging current of the condenser 28 causes a voltage drop across the resistance 3|, which is negative with respect to the cathode 48. r This voltage drop is nearly equal to'the voltage of the direct-current supply, as the battery l0l, at the first instant, but becomes smaller as the contherefore ocdenser 28 is charged. After the production of the light pulse, the condenser 28 becomes again charged, as from the battery l0! or other directcurrent supply, through the impedance 3|, in preparation for the next impulse.

Immediately after the condenser 28 discharges, the grid 50 is caused to be very negative with respect to the cathode 48 and, in this manner, the thyratron is prevented from starting as'the condenser 28 builds up and the anode becomes positive with respect to the cathode.

The thyratron trip circuit puts a high voltage on the starting band I00 in a sudden manner that makes the tube start reliably. The use of this starting-tube thyratron makes the mercury-arc stroboscope a practical and useful arrangement. The mercury-arc tube. may thus be started by a few microamperes of current in the grid circuit of the control tube,- and there is a negligible time delay between the current impulses to the grid and the starting of the light flashes.

One characteristic of the present invention is that the light produced by the tube 2 may be of much higher instantaneous intensity than is attainable with mercury tubes the light of which is continuous, instead of periodic.

Under the control of its trip circuit, through the flash transformer 30a, in the same manner as before described, a potential will be impressed upon the control electrode I00 in the control or starting path of the tube 1, to render the first normally non-conductive stroboscopic or rectifier tube I suddenly conductive. The principal current path of the tube 1 therefore becomes effec- .tive to charge the capacitor 26 from the directcurrent source 2|. The same type of current impulse that has before been described as initiated, during the discharge of the condenser 26, through the principal-current path of the tube 2, will therefore be initiated in the principal current path between the principal electrodes 4 and 6 of the tube 1, during the charging of this same condenser 26. Where repetitive or periodic flashing is desired, the potential will be impressed upon the starting or control electrode I00 of the tube 1 intermittently or periodically to initiate current pulses in the principal-current path of the tube '1, between its principal electrodes 4 and 6, intermittently or periodically.

The first stroboscopic or rectifier tube 1, however, is energized in advance of the second tube 2. This energization occurs for a predetermined interval of time during the pulse of current that is transmitted to the above-described condensercharging circuit to charge the condenser 26. A .flash is obtained in the first tube 1 during this charging of the condenser 26. It is not until after the condenser 26 has thus become charged that a pulse of current becomes transmitted through the starting-current path of the tube 2. Current flow is initiated, under the action of the capacitor 26, through the principal-current path, between the cathode 4 and the anode 6, of the tube 2. This results in a second flash, this time through the second tube 2.

The two before-described thyratron trip circuits, therefore, intermittently feed alternately into the primary windings 36, 36a of the transformers 30 and 300. that start the tubes 1 and 2. The tubes 2 and 1 are thus energized alternately to charge and discharge the condenser 26 alternately.

The thyratrons are tripped alternately by connecting their grids 50, 50a to a source I of alternating voltage by transformers ii and ila other means, to accomplish the desired result..

The circuit is especiallyeirective at high irequency since the time for deionization is long;

Modifications will occur to persons skilled in the art, and all such are considered to fall within the spirit and scope of the invention, as deilned in the appended claims.

What is claimed is:

1. In combination, an electric discharge device having a principal current path defined by a plurality of principal electrodes and a starting current path extending from a starting electrode for initiating current flow in said principal path, a capacitor connected between said principal electrodes. means for charging said capacitor including another discharge device having a plurality of principal electrodes and a control electrode, means for normally maintaining said last-named discharge device deenergized, means for intermittently applying a potential between said control electrode and one of the said last-named principal electrodes such that the said lastnamed discharg device is energized for a predetermined interval 01' time and during said interval of time transmits a pulse of current to charge said capacitor, and means for transmitting a pulse of current through said starting path after said capacitor has been charged to initiate current fiow through said principal path under the action of the potential of said capacitor.

2. In combination, an electric-discharge device having a principal-current path defined by a plurality of principal electrodes and a startingcurrent path extending from a starting electrode for initiating current fiow in said principal path, a capacitor connected between said principal electrodes, means for charging said capacitor including a normally deenergized discharge device having a plurality oi principal electrodes and a control electrode, means for periodically applying a potential between said control electrode and one of the said last-named principal electrodes such that the normally deenergized discharge device is energized for a predetermined interval of time and during said interval of time transmits a pulse of current to charge said capacitor, means for periodically transmitting a pulse of current through said starting path after said capacitor has been charged to initiate current flow through said principal path under the action or the potential of said capacitor, and means for varying the periodicity oi the transmission of the pulse of current.

3. In combination, an electric-discharge device having a principal-current path defined by a plurality of principal electrodes and a startingcurrent path extending from a starting electrode for initiating current fiow in said principal path, a capacitor connected between said principal electrodes, means for charging said capacitor including a normally deenergized discharge device having a plurality of principal electrodes and a control electrode, means for intermittently applying a potential between said control electrode and one of the said last-named principal electrodes such that the normally deenergized discharge device is energized i'or a predetermined interval of time and during said interval of time transmits a pulse of current to charge said capacitor, a second capacitor, means for charging the second capacitor, and means for connecting said second capacitor, after it has been so charged, to said starting path, whereby a pulse of current is transmitted through said starting path and current isinitiatedirom in said principal path.

10' I the first-named capacitor 4. In combination, an electric-discharge device having a principal-current path defined by a plurality or principal electrodes and a starting-current path extending from a starting electrode for initiating current fiow in said principal path, a capacitor connected between said principal electrodes, means for charging said capacitor including a normally deenergired discharge device having a plurality of principal electrodes and a control electrode, means for intermittently applying a potential between said control electrode and one of the said last-named principal electrodes such that the normally deenergized discharge device is energized for a predetermined interval of time and during said interval oi. time transmits a pulse of current to charge said capacitor, and means for transmitting a Pulse of current through said starting path after said capacitor has been charged to initiate current flow through said principal path under the action of the potential of said capacitor.

5. In combination, an electricdischarge device having a principal-current path defined by a plurality of principal electrodes and a startingcurrent path extending from a starting electrode for initiating current flow in said principal path, a capacitor connected between said principal electrodes, means for charging said capacitor including a normally deenergized discharge device having a plurality of principal electrodes and a control electrode, means for periodically applying a potential between said control electrode and one of the said last-named principal electrodes such that the normally deenergized discharge device is energized for a predetermined interval of time and during said interval of time transmits a pulse 01 current to charge said capacitor, and means for periodically transmitting a pulse 01' current through said starting path after said capacitor has been charged to initiate current fiow through said principal path under the action of the potential of said capacitor.

6. An electric system having, in combination, normally non-conductive gaseous-conductor means having a normally inefi'ective principalcurrent path defined by a plurality of principal electrodes and a control path extending from a control electrode for initiating pulses of current in the principal path, a capacitor, a source of potential, means connecting the capacitor and the gaseous-conductor means in the principal path to the source to charge the capacitor from the source when the principal path is eifective, means for intermittently impressing a potential upon the control electrode in the control path to render the gaseous-conductor means suddenly conductive intermittently in order to render the principal path intermittently effective to charge the capacitor intermittently from the source, thereby intermittently to initiate pulses of current in the principal path between the principal electrodes, and means whereby the pulses are caused to occur during times short compared to the intervals between the pulses.

'7. An electric system having, in combination, normally non-conductive gaseous-conductor means having a normally ineil'ective principalcurrent path defined by a plurality of principal electrodes at least one of which is composed of mercury and a starting-current path extending tor and the gaseous-conductor means in the principal path to the source to charge the capacitor from the source when the principal path is eflective, means for intermittently impressing pulses.

8. An electric system having, in combination, normally non-conductive gaseous-conductor means having a normally ineifective principalcurrent path defined by a plurality of principal electrodes, a capacitor, a source of potential, means connecting the capacitor and the gaseousconductor means in the principal path to the source to charge the capacitor from the source when the principal path is eflective, means for intermittently rendering the gaseous-conductor device suddenly conductive in order to render the principal path intermittently effective to charge the capacitor intermittently from the source, thereby intermittently to initiate pulses of current in the principal path between the principal conductive in order to render the principal path electrodes, and means whereby the pulses are caused to occur during times short compared to the intervals between the pulses.

9. A light-flash producer having, in combination, normally non-conductive gaseous-conductor means for producing light flashes of substantial illumination intensity having a normally ineflective principal-current path defined by a plurality of principal electrodes, a capacitor, a source of potential, means connecting the capacitor and the gaseous-conductor means in the principal path to the source to charge the capacitor from the source when the principal path is eflective,

and means for rendering the gaseous-conductor means suddenly conductive in order to render the principal path effective to charge the capacitor from the source, thereby to initiate a pulse of current in the principal path between the principal electrodes to produce suddenly a light flash of substantial illumination intensity.

10. A light-flash producer having, in combination, normally non-conductive gaseous-conductor means for producing fight flashes of substantial illumination intensity having a normally inefiective principal-current path defined by a plurality of principal electrodes and a control path extending from a control electrode for initiating a pulse of current in the principal path, a capacitor, a source of potential, means connecting the capacitor and the gaseous-conductor means in the principal path to the source to charge the capacitor from the source when the principal path is efiective, and means for impressing a potential upon the control electrode in the control path to render the gaseous-conductor means suddenly eflective to charge the capacitor from the source. thereby toinitiate a pulse or current in the principal path between the principal electrodes to produce suddenly a light flash of substantial illumination intensity.

11. A light-flash producer having, in combination, normally non-conductive gaseous-conductor means for producing light flashes of substantial illumination intensity having a normally ineflective principal-current path defined by a plurality of principal electrodes, a capacitor, a source or potential, means connecting the capacitor and the gaseous-conductor means in the principal path to the source to charge the capacitor from the source when the principal path is eiTectlve, means for intermittently rendering the gaseousconductor means suddenly conductive in order to render the principal path intermittently eifective to charge the capacitor intermittently from the source, thereby intermittently to initiate pulses of current in the principal path between the principal electrodes to produce suddenly light flashes of substantial illumination intensity, and means whereby the flashes are caused to occur during times short compared to the intervals between the flashes.

12. A light-flash producer having, in combination, normally non-conductive gaseous-conductor means for producing light flashes of substantial illumination intensity having a, normally inefl'ective principal-current path defined by a plurality of principal electrodes and a control path extending from a control electrode for initiating pulses of current in the principal path, a capacitor, a source of potential, means connecting the capacitor and the gaseous-conductor means in the principal path to the source to charge the capacitor from the source when the principal path is efiective, means for intermittently impressing a potential upon the control electrode in the control path to render the gaseous-conductor means suddenly conductive intermittently in order to render the principal path intermittently eflective to charge the capacitor intermittently from the source, thereby intermittently to initiate pulses of current in the principal path between the principal electrodes to produce suddenly light flashes of substantial illumination intensity, and means whereby the flashes are caused to occur during times short compared to the intervals between the flashes.

HAROLD E. EDGERTON.

REFERENCES crrnn The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,572 Miller Nov. 28, 1944 2,043,484 Miller June 9, 1936 2,073,247 Miller Mar. 9, 1937 2,310,092 Knowles et al Feb. 2, 1943 

